Method of selectively bonding braze powders to a surface

Abstract

A method for selectively adhering braze powders to a surface comprises applying a binder material to a surface, depositing a braze powder on the binder material, and then directing a laser beam onto the braze powder while the laser beam moves along a predetermined path relative to the surface. The laser beam selectively heats the braze powder and the binder material along the predetermined path such that the binder material is removed and the braze powder is sintered and bonded to the surface. Thus, a braze deposit is formed at one or more predetermined locations on the surface. After forming the braze deposit, excess braze powder and binder material, that is, the braze powder and binder material not selectively heated by the laser, are removed from the surface.

What is claimed is: 
     
       1. A method for selectively adhering braze powders to a surface, the method comprising:
 applying a binder material to a surface; 
 depositing a braze powder on the binder material; 
 directing a laser beam onto the braze powder while the laser beam moves along a predetermined path relative to the surface, the laser beam selectively heating the braze powder and the binder material along the predetermined path to remove the binder material and sinter and bond the braze powder to the surface, thereby forming a braze deposit at one or more predetermined locations on the surface, wherein a portion of the braze powder and the binder material are not selectively heated by the laser; and 
 after forming the braze deposit, removing the portion of the braze powder and the binder material not selectively heated by the laser from the surface. 
 
     
     
       2. The method of  claim 1 , wherein the binder material is applied to the surface by spraying, spin coating, dip coating, brushing, or rolling. 
     
     
       3. The method of  claim 1 , wherein the binder material applied to the surface has a thickness in a range from 0.01 mm to 1 mm. 
     
     
       4. The method of  claim 1 , wherein, during the selective heating, the binder material along the predetermined path is removed by pyrolysis or vaporization. 
     
     
       5. The method of  claim 1 , wherein the braze powder and the binder material are removed from the surface after forming the braze deposit by exposing the surface to a solvent. 
     
     
       6. The method of  claim 5 , wherein the exposure to the solvent comprises washing, immersion, or spraying. 
     
     
       7. The method of  claim 1 , wherein the predetermined path is a continuous path. 
     
     
       8. The method of  claim 1 , wherein the predetermined path is a discontinuous path, the laser beam being operated intermittently while moving. 
     
     
       9. The method of  claim 1 , wherein the surface is a discontinuous surface comprising surface regions separated by gaps, and wherein the braze deposit is formed on the surface regions. 
     
     
       10. The method of  claim 1 , wherein depositing the braze powder comprises spraying, scattering, or dusting the braze powder over the binder material, at least some fraction of the braze powder adhering to the binder material. 
     
     
       11. The method of  claim 1 , wherein the laser beam is generated by a laser selected from the group consisting of: gas laser, solid state laser, and fiber laser. 
     
     
       12. The method of  claim 1 , wherein the laser beam is a pulsed laser beam. 
     
     
       13. The method of  claim 1 , wherein the laser beam is a continuous laser beam. 
     
     
       14. The method of  claim 1 , wherein the laser beam is operated at a power level and a scan rate sufficient to remove the binder material and sinter the braze powder without melting the braze powder. 
     
     
       15. The method of  claim 1 , wherein the binder material and the braze powder along the predetermined path are selectively heated to a temperature in a range from 400° C. to 800° C. 
     
     
       16. The method of  claim 1 , wherein the surface is part of a first component comprising a metal alloy. 
     
     
       17. The method of  claim 1 , wherein the first component comprises part of an airfoil, a combustion liner, or a heat shield of a gas turbine engine. 
     
     
       18. The method of  claim 1 , wherein the braze powder comprises a nickel-based braze alloy, a titanium based-braze alloy, or an iron-based braze alloy. 
     
     
       19. A method of diffusion bonding comprising:
 the method of  claim 1 , wherein the surface is a first surface, and further comprising, after forming the braze deposit, assembling a first component comprising the first surface with a second component comprising a mating surface to form an assembly, the braze deposit on the first surface contacting the mating surface; and 
 exposing the assembly to a bonding temperature and a compressive force, thereby diffusion bonding the first component to the second component to form a monolithic third component comprising a bonded interface. 
 
     
     
       20. The method of  claim 19 , wherein the first component comprises a coversheet and the second component comprises a spar, the monolithic third component comprising an airfoil for use in a gas turbine engine.